METHYL-SUBSTITUTED BIPHENYL COMPOUNDS, THEIR PRODUCTION AND THEIR USE IN THE MANUFACTURE OF PLASTICIZERS

Description

FIELD

[0001] The disclosure relates to methyl-substituted biphenyl compounds, their production and their use in the manufacture of plasticizers.

BACKGROUND

[0002] Plasticizers are incorporated into a resin (usually a plastic or elastomer) to increase the flexibility, workability, or distensibility of the resin. The largest use of plasticizers is in the production of "plasticized" or flexible polyvinyl chloride (PVC) products. Typical uses of plasticized PVC include films, sheets, tubing, coated fabrics, wire and cable insulation and jacketing, toys, flooring materials such as vinyl sheet flooring or vinyl floor tiles, adhesives, sealants, inks, and medical products such as blood bags and tubing, and the like.

[0003] Other polymer systems that use small amounts of plasticizers include polyvinyl butyral, acrylic polymers, nylon, polyolefins, polyurethanes, and certain fluoroplastics. Plasticizers can also be used with rubber (although often these materials fall under the definition of extenders for rubber rather than plasticizers). A listing of the major plasticizers and their compatibilities with different polymer systems is provided in "Plasticizers," A. D. Godwin, in Applied Polymer Science 21st Century, edited by C. D. Craver and C. E. Carraher, Elsevier (2000); pp. 157-175.

[0004] The most important chemical class of plasticizers is phthalic acid esters, which accounted for about 84% worldwide of PVC plasticizer usage in 2009. However, there is an effort to decrease the use of phthalate esters as plasticizers in PVC, particularly in end uses where the product contacts food, such as bottle cap liners and sealants, medical and food films, or for medical examination gloves, blood bags, and IV delivery systems, flexible tubing, or for toys, and the like. As a result, there is a need for non-phthalate, mono- or diester plasticizers, particularly oxo-ester plasticizers, that can be made from low cost feeds and employ few manufacturing steps in order to have comparable economics with their phthalate counterparts. For these and most other uses of plasticized polymer systems, however, a successful substitute for phthalate esters has not yet been found.

[0005] One such suggested substitute for phthalates are esters based on cyclohexanoic acid. In the late 1990's and early 2000's, various compositions based on cyclohexanoate, cyclohexanedioates, and cyclohexanepolyoate esters were said to be useful for a range of goods from semi-rigid to highly flexible materials. See, for instance, WO 99/32427, WO 2004/046078, WO 2003/029339, U.S. Patent Publication No. 2006-0247461, and U.S. Patent No. 7,297,738.

[0006] Other suggested substitutes include esters based on benzoic acid (see, for instance, U.S. Patent No. 6,740,254) and polyketones, such as described in U.S. Pat. No. 6,777,514; and U.S. Patent Publication No. 2008-0242895. Epoxidized soybean oil, which has much longer alkyl groups (C₁₆ to C₁₈), has been tried as a plasticizer, but is generally used as a PVC stabilizer. Stabilizers are used in much lower concentrations than plasticizers. US Patent Publication No. 2010-0159177 discloses triglycerides with a total carbon number of the triester groups between 20 and 25, produced by esterification of glycerol with a combination of acids derived from the hydroformylation and subsequent oxidation of C₃ to C₉ olefins, having excellent compatibility with a wide variety of resins and that can be made with a high throughput.

[0007] Typically, the best that has been achieved with substitution of the phthalate ester with an alternative material is a flexible PVC article having either reduced performance or poorer processability. Thus, existing efforts to make phthalate-free plasticizer systems for PVC have not proven to be entirely satisfactory, and so this is still an area of intense research.

[0008] For example, in an article entitled "Esters of diphenic acid and their plasticizing properties", Kulev et al., Izvestiya Tomskogo Politekhnicheskogo Instituta (1961) 111, disclose that diisoamyl diphenate, bis(2-ethylhexyl) diphenate and mixed heptyl, octyl and nonyl diphenates can be prepared by esterification of diphenic acid, and allege that the resultant esters are useful as plasticizers for vinyl chloride. Similarly, in an article entitled "Synthesis of dialkyl diphenates and their properties", Shioda et al., Yuki Gosei Kagaku Kyokaishi (1959), 17, disclose that dialkyl diphenates of C₁ to C₈ alcohols, said to be useful as plasticizers for poly(vinyl chloride), can be formed by converting diphenic acid to diphenic anhydride and esterifying the diphenic anhydride. However, since these processes involve esterification of diphenic acid or anhydride, they necessarily result in 2,2'-substituted diesters of diphenic acid. Generally, such diesters having substitution on the 2-carbons have proven to be too volatile for use as plasticizers.

[0009] An alternative method of producing dialkyl diphenate esters having an increased proportion of the less volatile 3,3', 3,4' and 4,4' diesters has now been developed. In particular, it has been found that dimethylbiphenyl compounds containing significant amounts of the 3,3'-dimethyl, the 3,4'-dimethyl and the 4,4'-dimethyl isomers can be economically produced by hydroalkylation of toluene and/or xylene followed by dehydrogenation of the resulting (methylcyclohexyl)toluene and/or (dimethylcyclohexyl)xylene product. The resultant mixture can be used as a precursor in the production of biphenylester-based plasticizers by, for example, oxidizing the methyl-substituted biphenyl compounds to convert at least one of the methyl groups to a carboxylic acid group and then esterifying the carboxylic acid group with an alcohol, such as an oxo alcohol. In addition, depending on the catalyst employed, the hydroalkylation reaction exhibits low selectivity to fully saturated compounds, which are difficult to dehydrogenate to biphenyls, and low selectivity to heavies, which must be removed resulting in yield loss.

[0010] WO 2012/157749 A1 (US 2014/0058143 A1) discloses a hydroalkylation reaction to form a reaction solution comprising 3,3',4,4'-tetraalkylcyclohexyl benzene, followed by subjecting the reaction solution to a dehydrogenation reaction to obtain 3,3 ',4,4'-tetraalkylbiphenyl.

[0011] WO 2009/128984 A1 discloses the use of a catalyst system comprising a molecular sieve and at least one hydrogenation metal such as palladium, in the hydroalkylation of benzene.

[0012] Smirnitsky et a1. ("Hydrodimerization of benzene and alkylbenzene over polyfunctional zeolite catalysts", Studies in surface science and catalysis, vol. 84, 1994, pages 1813-1820) describe the hydrodimerization of benzene and alkylbenzene over polyfunctional zeolite catalysts.

[0013] Kamiyama et a1. ("Catalysts for the Hydroalkylation of Benzene, Toluene and Xylenes", Chemical and pharmaceutical bulletin, Pharmaceutical Society of Japan, vol. 29, 1981, pages 15-24) describe catalytic hydroalkylation of benzene over palladium and fused salt (NaCl-AlCl₃) under hydrogen pressure.

[0014] US 3,962,362 A discloses polyphenyls including biphenyl and terphenyl, which are prepared by hydroalkylation of a charge benzene, dehydrogenation of hydroalkylate, and separation of desired product polyphenyls.

SUMMARY

[0015] The present invention relates to a process as defined in claim 1. In the context of the present invention, in one aspect, the present disclosure is directed to a process for producing methyl-substituted biphenyl compounds, the process comprising:

(a) contacting a feed comprising at least one aromatic hydrocarbon selected from the group consisting of toluene, xylene and mixtures thereof with hydrogen in the presence of a hydroalkylation catalyst under conditions effective to produce a hydroalkylation reaction product comprising (methylcyclohexyl)toluenes and/or (dimethylcyclohexyl)xylenes; and

(b) dehydrogenating at least part of the hydroalkylation reaction product in the presence of a dehydrogenation catalyst under conditions effective to produce a dehydrogenation reaction product comprising a mixture of methyl-substituted biphenyl compounds.

[0016] In the context of the present invention, in another aspect, the present disclosure is directed to a process for producing biphenyl esters, the process comprising:

(a) contacting a feed comprising at least one aromatic hydrocarbon selected from the group consisting of toluene, xylene and mixtures thereof with hydrogen in the presence of a hydroalkylation catalyst under conditions effective to produce a hydroalkylation reaction product comprising (methylcyclohexyl)toluenes and/or (dimethylcyclohexyl)xylenes;

(b) dehydrogenating at least part of the hydroalkylation reaction product in the presence of a dehydrogenation catalyst under conditions effective to produce a dehydrogenation reaction product comprising a mixture of methyl-substituted biphenyl compounds;

(c) contacting at least part of the dehydrogenation reaction product with an oxidizing gas under conditions effective to convert at least part of the methyl-substituted biphenyl compounds to biphenyl carboxylic acids; and

(d) reacting the biphenyl carboxylic acids with one or more C₄ to C₁₄ alcohols under conditions effective to produce biphenyl esters.

[0017] According to the present invention, the hydroalkylation catalyst comprises an acidic component and a hydrogenation component. The acidic component comprises a molecular sieve of the MCM-22 family.

[0018] In the context of the present invention, in yet another aspect, the present disclosure is directed to a process for producing (methylcyclohexyl)toluene, the process comprising:

(a) contacting a feed comprising toluene with hydrogen in the presence of a hydroalkylation catalyst under conditions effective to produce a hydroalkylation reaction product comprising (methylcyclohexyl)toluene, wherein the hydroalkylation catalyst comprises a molecular sieve of the MCM-22 family and a hydrogenation metal.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 

Figure 1 is a bar graph comparing the amount of di(methylcyclohexyl)toluenes produced in the hydroalkylation of toluene over the catalysts of Examples 1 to 4.

Figure 2 is a graph of toluene conversion against time on stream (TOS) in the hydroalkylation of toluene over the Pd-MCM-49 catalyst of Example 1.

Figure 3 is a graph of toluene conversion against time on stream (TOS) in the hydroalkylation of toluene over the Pd-beta catalyst of Example 2.

Figure 4 is a graph of toluene conversion against time on stream (TOS) in the hydroalkylation of toluene over the Pd-Y catalyst of Example 3.

Figure 5 is a graph of toluene conversion against time on stream (TOS) in the hydroalkylation of toluene over the Pd-WO₃/ZrO₂ catalyst of Example 4.

Figure 6 is a bar graph comparing the reaction effluents produced by the non-selective dehydrogenation of the hydroalkylation products of Examples 1 and 2.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] The present disclosure relates to the production of methyl substituted biphenyl compounds by the catalytic hydroalkylation of toluene and/or xylene followed by dehydrogenation of at least part of the hydroalkylation reaction product. Depending on the catalyst employed in the hydroalkylation reaction, the hydroalkylation process is selective to the production of the desired (methylcyclohexyl)toluenes and/or (dimethylcyclohexyl)xylenes without excessive production of heavies and fully saturated rings. In addition, the dimethylbiphenyl product of the dehydrogenation reaction contains significant amounts of the 3,3'-dimethyl, the 3,4'-dimethyl and the 4,4'-dimethyl compounds making the product an attractive precursor in the production of biphenylester-based plasticizers.

Hydroalkylation of toluene and/or xylene

[0021] Hydroalkylation is a two-stage catalytic reaction in which an aromatic compound is partially hydrogenated to produce a cyclic olefin, which then reacts, in situ, with the aromatic compound to produce a cycloalkylaromatic product. In the present process, the aromatic compound comprises toluene and/or xylene and the cycloalkylaromatic product comprises a mixture of (methylcyclohexyl)toluene and/or (dimethylcyclohexyl)xylene isomers. In the case of toluene, the desired reaction may be summarized as follows:

[0022] Among the competing reactions is further hydrogenation of the cyclic olefin intermediate and/or the cycloalkylaromatic product to produce fully saturated rings. In the case of toluene as the hydroalkylation feed, further hydrogenation can produce methylcyclohexane and dimethylbicyclohexane compounds. Although these by-products can be converted back to feed (toluene) and to the product ((methylcyclohexyl)toluene and dimethylbiphenyl) via dehydrogenation, this involves an endothermic reaction requiring high temperatures (>375°C) to obtain high conversion. This not only makes the reaction costly but can also lead to further by-product formation and hence yield loss. It is therefore desirable to employ a hydroalkylation catalyst that exhibits low selectivity towards the production of fully saturated rings.

[0023] Another competing reaction is dialkylation in which the (methylcyclohexyl)toluene product reacts with further methylcyclohexene to produce di(methylcyclohexyl)toluene. Again this by-product can be converted back to (methylcyclohexyl)toluene, in this case by transalkylation. However, this process requires the use of an acid catalyst at temperatures above 160°C and can lead to the production of additional by-products, such as di(methylcyclopentyl)toluenes, cyclohexylxylenes and cyclohexylbenzene. It is therefore desirable to employ a hydroalkylation catalyst that exhibits low selectivity towards di(methylcyclohexyl)toluene and other heavy by-products.

[0024] The catalyst employed in the hydroalkylation reaction is a bifunctional catalyst comprising a hydrogenation component and a solid acid alkylation component, typically a molecular sieve. The catalyst may also include a binder such as clay, silica and/or metal oxides. The latter may be either naturally occurring or in the form of gelatinous precipitates or gels including mixtures of silica and metal oxides. Naturally occurring clays which can be used as a binder include those of the montmorillonite and kaolin families, which families include the subbentonites and the kaolins commonly known as Dixie, McNamee, Georgia and Florida clays or others in which the main mineral constituent is halloysite, kaolinite, dickite, nacrite or anauxite. Such clays can be used in the raw state as originally mined or initially subjected to calcination, acid treatment or chemical modification. Suitable metal oxide binders include silica, alumina, zirconia, titania, silica-alumina, silica-magnesia, silica-zirconia, silica-thoria, silica-beryllia, silica-titania as well as ternary compositions such as silica-alumina-thoria, silica-alumina-zirconia, silica-alumina-magnesia and silica-magnesia-zirconia.

[0025] Any known hydrogenation metal or compound thereof can be employed as the hydrogenation component of the catalyst, although suitable metals include palladium, ruthenium, nickel, zinc, tin, and cobalt, with palladium being particularly advantageous. In certain embodiments, the amount of hydrogenation metal present in the catalyst is between about 0.05 and about 10 wt %, such as between about 0.1 and about 5 wt %, of the catalyst.

[0026] In the present disclosure the solid acid alkylation component comprises a large pore molecular sieve having a Constraint Index (as defined in U.S. Patent No. 4,016,218) less than 2. Suitable large pore molecular sieves include zeolite beta, zeolite Y, Ultrastable Y (USY), Dealuminized Y (Deal Y), mordenite, ZSM-3, ZSM-4, ZSM-18, and ZSM-20. Zeolite ZSM-14 is described in U.S. Patent No. 3,923,636. Zeolite ZSM-20 is described in U.S. Patent No. 3,972,983. Zeolite Beta is described in U.S. Patent Nos. 3,308,069, and Re. No. 28,341. Low sodium Ultrastable Y molecular sieve (USY) is described in U.S. Patent Nos. 3,293,192 and 3,449,070. Dealuminized Y zeolite (Deal Y) may be prepared by the method found in U.S. Patent No. 3,442,795. Zeolite UHP-Y is described in U.S. Patent No. 4,401,556. Mordenite is a naturally occurring material but is also available in synthetic forms, such as TEA-mordenite (i.e., synthetic mordenite prepared from a reaction mixture comprising a tetraethylammonium directing agent). TEA-mordenite is disclosed in U.S. Patent Nos. 3,766,093 and 3,894,104.

[0027] According to the present invention, the solid acid alkylation component comprises a molecular sieve of the MCM-22 family. The term "MCM-22 family material" (or "material of the MCM-22 family" or "molecular sieve of the MCM-22 family"), as used herein, includes one or more of:

• molecular sieves made from a common first degree crystalline building block unit cell, which unit cell has the MWW framework topology. (A unit cell is a spatial arrangement of atoms which if tiled in three-dimensional space describes the crystal structure. Such crystal structures are discussed in the "Atlas of Zeolite Framework Types", Fifth edition, 2001);
• molecular sieves made from a common second degree building block, being a 2-dimensional tiling of such MWW framework topology unit cells, forming a monolayer of one unit cell thickness, preferably one c-unit cell thickness;
• molecular sieves made from common second degree building blocks, being layers of one or more than one unit cell thickness, wherein the layer of more than one unit cell thickness is made from stacking, packing, or binding at least two monolayers of one unit cell thickness. The stacking of such second degree building blocks can be in a regular fashion, an irregular fashion, a random fashion, or any combination thereof; and
• molecular sieves made by any regular or random 2-dimensional or 3-dimensional combination of unit cells having the MWW framework topology.

[0028] Molecular sieves of MCM-22 family generally have an X-ray diffraction pattern including d-spacing maxima at 12.4±0.25, 6.9±0.15, 3.57±0.07 and 3.42±0.07 Angstrom. The X-ray diffraction data used to characterize the material are obtained by standard techniques using the K-alpha doublet of copper as the incident radiation and a diffractometer equipped with a scintillation counter and associated computer as the collection system. Molecular sieves of MCM-22 family include MCM-22 (described in U.S. Patent No. 4,954,325), PSH-3 (described in U.S. Patent No. 4,439,409), SSZ-25 (described in U.S. Patent No. 4,826,667), ERB-1 (described in European Patent No. 0293032), ITQ-1 (described in U.S. Patent No 6,077,498), ITQ-2 (described in International Patent Publication No. WO97/17290), MCM-36 (described in U.S. Patent No. 5,250,277), MCM-49 (described in U.S. Patent No. 5,236,575), MCM-56 (described in U.S. Patent No. 5,362,697) and mixtures thereof.

[0029] In addition to the toluene and/or xylene and hydrogen, a diluent, which is substantially inert under hydroalkylation conditions, may be included in the feed to the hydroalkylation reaction. In certain embodiments, the diluent is a hydrocarbon, in which the desired cycloalkylaromatic product is soluble, such as a straight chain paraffinic hydrocarbon, a branched chain paraffinic hydrocarbon, and/or a cyclic paraffinic hydrocarbon. Examples of suitable diluents are decane and cyclohexane. Although the amount of diluent is not narrowly defined, desirably the diluent is added in an amount such that the weight ratio of the diluent to the aromatic compound is at least 1:100; for example at least 1: 10, but no more than 10:1, desirably no more than 4:1.

[0030] In one embodiment, the aromatic feed to the hydroalkylation reaction also includes benzene and/or one or more alkylbenzenes different from toluene and xylene. Suitable alkylbenzenes may have one or more alkyl groups with up to 4 carbon atoms and include, by way of example, ethylbenzene, cumene, and unseparated C₆-C₈ or C₇-C₈ or C₇-C₉ streams.

[0031] The hydroalkylation reaction can be conducted in a wide range of reactor configurations including fixed bed, slurry reactors, and/or catalytic distillation towers. In addition, the hydroalkylation reaction can be conducted in a single reaction zone or in a plurality of reaction zones, in which at least the hydrogen is introduced to the reaction in stages. Suitable reaction temperatures are between about 100°C and about 400°C, such as between about 125°C and about 250°C, while suitable reaction pressures are between about 100 and about 7,000 kPa, such as between about 500 and about 5,000 kPa. The molar ratio of hydrogen to aromatic feed is typically from about 0.15:1 to about 15:1.

[0032] In the present process, it is found that MCM-22 family molecular sieves are particularly active and stable catalysts for the hydroalkylation of toluene or xylene. In addition, catalysts containing MCM-22 family molecular sieves exhibit improved selectivity to the 3,3'-dimethyl, the 3,4'-dimethyl, the 4,3'-dimethyl and the 4,4'-dimethyl isomers in the hydroalkylation product, while at the same time reducing the formation of fully saturated and heavy by-products. For example, using an MCM-22 family molecular sieve with a toluene feed, it is found that the hydroalkylation reaction product may comprise:

• at least 60 wt%, such as at least 70 wt%, for example at least 80 wt% of the 3,3, 3,4, 4,3 and 4,4-isomers of (methylcyclohexyl)toluene based on the total weight of all the (methylcyclohexyl)toluene isomers;
• less than 30 wt% of methylcyclohexane and less than 2% of dimethylbicyclohexane compounds; and
• less than 1 wt% of compounds containing in excess of 14 carbon atoms.

[0033] Similarly, with a xylene feed, the hydroalkylation reaction product may comprise less than 1 wt% of compounds containing in excess of 16 carbon atoms.

[0034] By way of illustration, the 3,3, 3,4 4,3 and 4,4-isomers of (methylcyclohexyl)toluene are illustrated in formulas F1 to F4, respectively:

[0035] In contrast, when the methyl group is located in the 1-position (quaternary carbon) on the cyclohexyl ring, ring isomerization can occur forming (dimethylcyclopentyl)toluene and (ethylcyclopentyl)toluene which, on dehydrogenation, will generate diene by-products which are difficult to separate from the desired product and will also inhibit the subsequent oxidation reaction. In the oxidation and esterification steps, different isomers have different reactivity. Thus, para-isomers are more reactive than meta-isomers which are more reactive than ortho-isomers. Also in the dehydrogenation step, the presence of a methyl group in the 2 position on either the cyclohexyl or phenyl ring is a precursor for the formation of fluorene and methyl fluorene. Fluorene is difficult to separate from the dimethylbiphenyl product and causes problems in the oxidation step and also in the plasticizers performance. It is therefore advantageous to minimize the formation of isomers which have a methyl group in the ortho, 2 and benzylic positions.

Dehydrogenation of Hydroalkylation Product

[0036] The major components of the hydroalkylation reaction effluent are (methylcyclohexyl)toluenes and/or (dimethylcyclohexyl)xylenes, unreacted aromatic feed (toluene and/or xylene) and fully saturated single ring by-products (methylcyclohexane and dimethylcyclohexane). The unreacted feed and light by-products can readily be removed from the reaction effluent by, for example, distillation. The unreacted feed can then be recycled to the hydroalkylation reactor, while the saturated by-products can be dehydrogenated to produce additional recyclable feed.

[0037] The remainder of the hydroalkylation reaction effluent, composed mainly of (methylcyclohexyl)toluenes and/or (dimethylcyclohexyl)xylenes, is then dehydrogenated to produce the corresponding methyl-substituted biphenyl compounds. The dehydrogenation is conveniently conducted at a temperature from about 200°C to about 600°C and a pressure from about 100 kPa to about 3550 kPa (atmospheric to about 500 psig) in the presence of dehydrogenation catalyst. A suitable dehydrogenation catalyst comprises one or more elements or compounds thereof selected from Group 10 of the Periodic Table of Elements, for example platinum, on a support, such as silica, alumina or carbon nanotubes. In one embodiment, the Group 10 element is present in amount from 0.1 to 5 wt % of the catalyst. In some cases, the dehydrogenation catalyst may also include tin or a tin compound to improve the selectivity to the desired methyl-substituted biphenyl product. In one embodiment, the tin is present in amount from 0.05 to 2.5 wt % of the catalyst.

[0038] As used herein, the numbering scheme for the Periodic Table Groups is as disclosed in Chemical and Engineering News, 63(5), 27 (1985).

[0039] Particularly using an MCM-22 family-based catalyst for the upstream hydroalkylation reaction, the product of the dehydrogenation step comprises methyl-substituted biphenyl compounds in which the concentration of the 3,3-, 3,4- and 4,4-dimethyl isomers is at least 50 wt%, such as at least 60 wt%, for example at least 70 wt% based on the total weight of methyl-substituted biphenyl isomers. In addition, the product may contain less than 10 wt%, such as less than 5 wt%, for example less than 3 wt% of methyl biphenyl compounds and less than 5 wt%, such as less than 3 wt%, for example less than 1 wt% of fluorene and methyl fluorenes combined.

Production of Biphenyl Esters

[0040] The methyl-substituted biphenyl compounds produced by the dehydrogenation reaction can readily be converted ester plasticizers by a process comprising oxidation to produce the corresponding carboxylic acids followed by esterification with an alcohol.

[0041] The oxidation can be performed by any process known in the art, such as by reacting the methyl-substituted biphenyl compounds with an oxidant, such as oxygen, ozone or air, or any other oxygen source, such as hydrogen peroxide, in the presence of a catalyst at temperatures from 30°C to 300°C, such as from 60°C to 200°C. Suitable catalysts comprise Co or Mn or a combination of both metals.

[0042] The resulting carboxylic acids can then be esterified to produce biphenyl ester plasticizers by reaction with one or more C₄ to C₁₄ alcohols. Suitable esterification conditions are well-known in the art and include, but are not limited to, temperatures of 0-300°C and the presence or absence of homogeneous or heterogeneous esterification catalysts, such as Lewis or Bronsted acid catalysts. Suitable alcohols are "oxo-alcohols", by which is meant an organic alcohol, or mixture of organic alcohols, which is prepared by hydroformylating an olefin, followed by hydrogenation to form the alcohols. Typically, the olefin is formed by light olefin oligomerization over heterogeneous acid catalysts, which olefins are readily available from refinery processing operations. The reaction results in mixtures of longer-chain, branched olefins, which subsequently form longer chain, branched alcohols, as described in U.S. Pat. No. 6,274,756. Another source of olefins used in the OXO process are through the oligomerization of ethylene, producing mixtures of predominately straight chain alcohols with lesser amounts of lightly branched alcohols.

[0043] The biphenyl ester plasticizers of the present application find use in a number of different polymers, such as vinyl chloride resins, polyesters, polyurethanes, ethylene-vinyl acetate copolymers, rubbers, poly(meth)acrylics and mixtures thereof.

[0044] The invention will now be more particularly described with reference to the accompanying drawings and the following non-limiting Examples.

Example 1: Synthesis of 0.3%Pd/MCM-49 Catalyst

[0045] 80 parts MCM-49 zeolite crystals are combined with 20 parts pseudoboehmite alumina, on a calcined dry weight basis. The MCM-49 and pseudoboehmite alumina dry powder is placed in a muller and mixed for about 10 to 30 minutes. Sufficient water and 0.05% polyvinyl alcohol is added to the MCM-49 and alumina during the mixing process to produce an extrudable paste. The extrudable paste is formed into a 1/20 inch (0.13 cm) quadrulobe extrudate using an extruder and the resulting extrudate is dried at a temperature ranging from 250°F to 325°F (120°C to 163°C). After drying, the dried extrudate is heated to 1000°F (538°C) under flowing nitrogen. The extrudate is then cooled to ambient temperature and humidified with saturated air or steam.

[0046] After the humidification, the extrudate is ion exchanged with 0.5 to 1 N ammonium nitrate solution. The ammonium nitrate solution ion exchange is repeated. The ammonium nitrate exchanged extrudate is then washed with deionized water to remove residual nitrate prior to calcination in air. After washing the wet extrudate, it is dried. The exchanged and dried extrudate is then calcined in a nitrogen/air mixture to a temperature 1000°F (538°C). Afterwards, the calcined extrudate is cooled to room temperature. The 80% MCM-49, 20% Al₂O₃ extrudate was incipient wetness impregnated with a palladium (II) chloride solution (target: 0.30% Pd) and then dried overnight at 121°C. The dried catalyst was calcined in air at the following conditions: 5 volumes air per volume catalyst per minute, ramp from ambient to 538°C at 1°C/min and hold for 3 hours.

Example 2: Synthesis of 0.3%Pd/Beta Catalyst

[0047] 80 parts beta zeolite crystals are combined with 20 parts pseudoboehmite alumina, on a calcined dry weight basis. The beta and pseudoboehmite are mixed in a muller for about 15 to 60 minutes. Sufficient water and 1.0% nitric acid is added during the mixing process to produce an extrudable paste. The extrudable paste is formed into a 1.27 mm (1/20 inch) quadrulobe extrudate using an extruder. After extrusion, the 1.27 mm (1/20 inch) quadrulobe extrudate is dried at a temperature ranging from 250°F to 325°F (120°C to 163°C). After drying, the dried extrudate is heated to 1000°F (538°C) under flowing nitrogen and then calcined in air at a temperature of 1000°F (538°C). Afterwards, the calcined extrudate is cooled to room temperature. The 80% Beta, 20% Al₂O₃ extrudate was incipient wetness impregnated with a tetraammine palladium (II) nitrate solution (target: 0.30% Pd) and then dried overnight at 121°C. The dried catalyst was calcined in air at the following conditions: 5 volumes air per volume catalyst per minute, ramp from ambient to 538°C at 1°C/min and hold for 3 hours.

Example 3: Synthesis of 0.3%Pd/USY Catalyst

[0048] 80 parts Zeolyst CBV-720 ultrastable Y zeolite crystals are combined with 20 parts pseudoboehmite alumina on a calcined dry weight basis. The USY and pseudoboehmite are mixed for about 15 to 60 minutes. Sufficient water and 1.0% nitric acid is added during the mixing process to produce an extrudable paste. The extrudable paste is formed into a 1.27 mm (1/20 inch) quadrulobe extrudate using an extruder. After extrusion, the 1.27 mm (1/20 inch) quadrulobe extrudate is dried at a temperature ranging from 250°F to 325°F (120°C to 163°C). After drying, the dried extrudate is heated to 1000°F (538°C) under flowing nitrogen and then calcined in air at a temperature of 1000°F (538°C). The 80% CBV-720 USY, 20% Al₂O₃ extrudate was incipient wetness impregnated with a palladium (II) chloride solution (target: 0.30% Pd) and then dried overnight at 121°C. The dried catalyst was calcined in air at the following conditions: 5 volumes air per volume catalyst per minute, ramp from ambient to 538°C at 1°C/min and hold for 3 hours.

Example 4: Synthesis of 0.3%Pd/W-Zr Catalyst

[0049] A WO₃/ZrO₂ extrudate (11.5% W, balance Zr) 1/16" cylinder was obtained from Magnesium Elektron in the form of a 1/16 inch (0.16 cm) diameter extrudate. The WO₃/ZrO₂ extrudate was calcined in air for 3 hours at 538°C. On cooling, the calcined extrudate was incipient wetness impregnated with a palladium (II) chloride solution (target: 0.30% Pd) and then dried overnight at 121°C. The dried catalyst was calcined in air at the following conditions: 5 volumes air per volume catalyst per minute, ramp from ambient to 538°C at 1°C/min and hold for 3 hours.

Example 5: Hydroalkylation Catalyst Testing

[0050] Each of the catalyst of Examples 1 to 4 was then tested in the hydroalkylation of a toluene feed using the reactor and process described below.

[0051] The reactor comprised a stainless steel tube having an outside diameter of: 3/8 inch (0.95 cm), a length of 20.5 inch (52 cm) and a wall thickness of 0.35 inch (0.9 cm). A piece of stainless steel tubing having a length of 8% inch (22 cm) and an outside diameter of: 3/8 inch (0.95 cm) and a similar length of ¼ inch (0.6 cm) tubing of were used in the bottom of the reactor (one inside of the other) as a spacer to position and support the catalyst in the isothermal zone of the furnace. A ¼ inch (0.6 cm) plug of glass wool was placed on top of the spacer to keep the catalyst in place. A 1/8 inch (0.3 cm) stainless steel thermo-well was placed in the catalyst bed to monitor temperature throughout the catalyst bed using a movable thermocouple.

[0052] The catalyst was sized to 20/40 sieve mesh or cut to 1:1 length to diameter ratio, dispersed with quartz chips (20/40 mesh) then loaded into the reactor from the top to a volume of 5.5 cc. The catalyst bed typically was 15 cm. in length. The remaining void space at the top of the reactor was filled with quartz chips, with a ¼ plug of glass wool placed on top of the catalyst bed being used to separate quartz chips from the catalyst. The reactor was installed in a furnace with the catalyst bed in the middle of the furnace at a pre-marked isothermal zone. The reactor was then pressure and leak tested typically at 300 psig (2170 kPa).

[0053] The catalyst was pre-conditioned in situ by heating to 25°C to 240°C with H₂ flow at 100 cc/min and holding for 12 hours. A 500 cc ISCO syringe pump was used to introduce a chemical grade toluene feed to the reactor. The feed was pumped through a vaporizer before flowing through heated lines to the reactor. A Brooks mass flow controller was used to set the hydrogen flow rate. A Grove "Mity Mite" back pressure controller was used to control the reactor pressure typically at 150 psig (1135 kPa). GC analyses were taken to verify feed composition. The feed was then pumped through the catalyst bed held at the reaction temperature of 120°C to 180°C at a WHSV of 2 and a pressure of 15-200 psig (204-1480 kPa). The liquid products exiting the reactor flowed through heated lines routed to two collection pots in series, the first pot being heated to 60°C and the second pot cooled with chilled coolant to about 10°C. Material balances were taken at 12 to 24 hrs intervals. Samples were taken and diluted with 50% ethanol for analysis. An Agilent 7890 gas chromatograph with FID detector was used for the analysis. The non-condensable gas products were routed to an on line HP 5890 GC.
The analysis is done on an Agilent 7890 GC with 150 vial sample tray.
Inlet Temp: 220°C
Detector Temp: 240°C (Col + make up = constant)
Temp Program: Initial temp 120°C hold for 15 min., ramp at 2°C/min to 180°C, hold 15 min; ramp at 3°C/min. to 220°C and hold till end.
Column Flow: 2.25 ml/min. (27 cm/sec); Split mode, Split ratio 100:1
Injector: Auto sampler (0.2 µl).
Column Parameters:
Two columns joined to make 120 Meters (coupled with Agilent ultimate union, deactivated.
Column # Front end: Supelco β-Dex 120 ; 60m x 0.25 mm x 0.25 µm film joined to Column # 2 back end:y- Dex 325: 60 m x0.25 mm x 0.25 µm film.

[0054] The results of the hydroalkylation testing are summarized in Figures 1 to 4 and Table 1.

Table 1

Example	Catalyst	Toluene conversion	Selectivity to methylcyclohexane	Selectivity to dimethylbi(cyclohexane)
1	0.3%Pd-MCM49	37%	23%	1.40%
2	0.3% Pd/Beta	40%	65%	1.60%
3	0.3% Pd/Y	80%	75%	3.70%
4	0.3% WO3/ZrO2	13%	35%	1.75%

[0055] As can be seen from Table 1, although the Pd/MCM-49 catalyst is less active than the Pd/Y catalyst, it has much lower selectivity towards the production of the fully saturated by-products, methylcyclohexane and dimethylbi(cyclohexane) than either Pd/Y or Pd/beta. In addition, the data shown in Figure 1 clearly demonstrate that Pd/MCM-49 provides the lowest yield loss, less than 1 wt% of total converted feed, to dialkylate products. The data shown in Figures 2 to 5 demonstrate that Pd/MCM-49 has improved stability and catalyst life as compared with the other catalysts tested. It is believed that the stability is related to the formation of heavies which remain on the surface of the catalyst and react further to create coke which prevents the access to the acid and hydrogenation sites.

Example 6: Dehydrogenation of Methylcyclohexyltoluene

[0056] The same reactor, catalyst and analytical configuration as described above was used to perform dehydrogenation tests on the conversion products produced in Example 5 from the Pd/MCM-49 and Pd/beta catalysts of Examples 1 and 2, except each dehydrogenation catalyst was pre-conditioned in situ by heating to 375°C to 460°C with H₂ flow at 100 cc/min and holding for 2 hours. In addition, in the dehydrogenation tests the catalyst bed was held at the reaction temperature of 375°C to 460°C at a WHSV of 2 and a pressure of 100 psig (790 kPa).

[0057] In a first set of tests, the dehydrogenation was conducted at a temperature of 425°C using a selective dehydrogenation catalyst comprising bimetallic catalyst e.g., Pt/Sn, on a support. The results of the tests are summarized in Table 2 below:

Table 2

	MCM-49 HA product over selective dehydrogenation catalyst	Beta HA product over selective dehydrogenation catalyst
3-methyl biphenyl	0.70%	2.47%
4-methyl biphenyl	0.79%	4.98%
2,2 dimethyl biphenyl	1.21%	1.04%
2,3 dimethyl biphenyl	9.52%	8.42%
2,4 dimethyl biphenyl	13.14%	12.64%
3,3 dimethyl biphenyl	15.98%	13.21%
3,4 dimethyl biphenyl	39.64%	36.26%
4,4 dimethyl biphenyl	18.76%	18.19%
fluorene	0.00%	0.93%
methyl fluorenes	0.26%	1.87%

[0058] In a second set of tests, the dehydrogenation was conducted at a temperature of 425°C using a non-selective dehydrogenation catalyst comprising Pt on a support. The results of the tests are summarized in Figure 6.

[0059] The data clearly shows that dehydrogenation of the MCM-49 hydroalkylation products provides less mono methyl biphenyl, less of the 2',3 and 2',4 dimethyl biphenyl isomers which are the precursor for the formation of fluorene and methyl fluorene and much less the fluorene and methyl fluorene as compared with dehydrogenation of the zeolite beta hydroalkylation products.

Claims

1. A process for producing methyl-substituted biphenyl compounds, the process comprising:

(a) contacting a feed comprising at least one aromatic hydrocarbon selected from the group consisting of toluene and mixtures of toluene and xylene with hydrogen in the presence of a hydroalkylation catalyst comprising an acidic component and a hydrogenation component, under conditions effective to produce a hydroalkylation reaction product comprising (methylcyclohexyl)toluenes; and

(b) dehydrogenating at least part of the hydroalkylation reaction product in the presence of a dehydrogenation catalyst under conditions effective to produce a dehydrogenation reaction product comprising a mixture of methyl-substituted biphenyl compounds,

wherein the acidic component of the hydroalkylation catalyst comprises a molecular sieve, wherein the molecular sieve comprises a molecular sieve of the MCM-22 family.

2. The process of claim 1, further comprising:

(c) contacting at least part of the dehydrogenation reaction product with an oxidant under conditions effective to convert at least part of the methyl-substituted biphenyl compounds to biphenyl carboxylic acids; and

(d) reacting the biphenyl carboxylic acids with one or more C₄ to C₁₄ alcohols under conditions effective to produce biphenyl esters.

3. The process of any one of claims 1 to 2, wherein the hydrogenation component of the hydroalkylation catalyst is selected from the group consisting of palladium, ruthenium, nickel, zinc, tin, cobalt and compounds and mixtures thereof.

4. The process of any one of claims 1 to 3, wherein the conditions in the contacting (a) include a temperature from 100°C to 400°C and a pressure from 100 to 7,000 kPa.

5. The process of any one of claims 1 to 4, wherein the molar ratio of hydrogen to aromatic feed supplied to the contacting (a) is from 0.15:1 to 15:1.

6. The process of any one of claims 1 to 5, wherein the aromatic hydrocarbon is toluene and the hydroalkylation reaction product comprises less than 30 wt% of methylcyclohexane and less than 2% of dimethylbi(cyclohexane) compounds.

7. The process of any one of claims 1 to 6, wherein the aromatic hydrocarbon is toluene and the hydroalkylation reaction product comprises less than 1 wt% of compounds containing in excess of 14 carbon atoms.

8. The process of any one of claims 1 to 7, wherein the feed further comprises benzene and/or at least one alkylbenzene different from toluene and xylene.

9. The process of any one of claims 1 to 8, wherein the dehydrogenation catalyst comprises an element or compound thereof selected from Group 10 of the Periodic Table of Elements.

10. The process of any one of claims 1 to 9, wherein the dehydrogenation conditions in
(b) include a temperature from 200°C to 600°C and a pressure from 100 kPa to 3550 kPa (atmospheric to 500 psig).

Ansprüche

1. Verfahren zur Produktion von methylsubstituierten Biphenylverbindungen, bei dem

(a) ein Einsatzmaterial, das mindestens einen aromatischen Kohlenwasserstoff ausgewählt aus der Gruppe bestehend aus Toluol und Mischungen von Toluol und Xylol umfasst, in Gegenwart von Hydroalkylierungskatalysator, der eine saure Komponente und eine Hydrierkomponente umfasst, unter Bedingungen mit Wasserstoff in Kontakt gebracht wird, die wirksam sind, um Hydroalkylierungsreaktionsprodukt zu produzieren, welches (Methylcyclohexyl)toluole umfasst,

(b) mindestens ein Teil des Hydroalkylierungsreaktionsprodukts in Gegenwart eines Dehydrierungskatalysators unter Bedingungen dehydriert wird, die wirksam sind, um ein Dehydrierungsreaktionsprodukt zu produzieren, das eine Mischung aus methylsubstituierten Biphenylverbindungen umfasst,

wobei die saure Komponente des Hydroalkylierungskatalysators Molekularsieb umfasst, wobei das Molekularsieb ein Molekularsieb der Familie MCM-22 umfasst.

2. Verfahren nach Anspruch 1, bei dem ferner

(c) mindestens ein Teil des Dehydrierungsreaktionsprodukts unter Bedingungen mit einem Oxidationsmittel in Kontakt gebracht wird, die wirksam sind, um mindestens einen Teil der methylsubstituierten Biphenylverbindungen in Biphenylcarbonsäuren umzuwandeln, und

(d) die Biphenylcarbonsäuren unter Bedingungen mit einem oder mehreren C₄- bis C₁₄-Alkoholen umgesetzt werden, die wirksam sind, um Biphenylester zu produzieren.

3. Verfahren nach einem der Ansprüche 1 bis 2, bei dem die Hydrierkomponente des Hydroalkylierungskatalysators ausgewählt ist aus der Gruppe bestehend aus Palladium, Ruthenium, Nickel, Zink, Zinn, Kobalt und Verbindungen und Mischungen davon.

4. Verfahren nach einem der Ansprüche 1 bis 3, bei dem die Bedingungen, unter denen in (a) in Kontakt gebracht wird, eine Temperatur von 100°C bis 400°C und einem Druck von 100 kPa bis 7000 kPa einschließen.

5. Verfahren nach einem der Ansprüche 1 bis 4, bei dem das molare Verhältnis von Wasserstoff zu aromatischem Einsatzmaterial, welche in (a) zugeführt werden, um in Kontakt gebracht zu werden, 0,15:1 bis 15:1 beträgt.

6. Verfahren nach einem der Ansprüche 1 bis 5, bei dem der aromatische Kohlenwasserstoff Toluol ist und das Hydroalkylierungsreaktionsprodukt weniger als 30 Gew.% Methylcyclohexan und weniger als 2 % Dimethylbi(cyclohexan)verbindungen umfasst.

7. Verfahren nach einem der Ansprüche 1 bis 6, bei dem der aromatische Kohlenwasserstoff Toluol ist und das Hydroalkylierungsreaktionsprodukt weniger als 1 Gew.% Verbindungen umfasst, die mehr als 14 Kohlenstoffatome enthalten.

8. Verfahren nach einem der Ansprüche 1 bis 7, bei dem das Einsatzmaterial ferner Benzol und/oder mindestens ein Alkylbenzol umfasst, das sich von Toluol und Xylol unterscheidet.

9. Verfahren nach einem der Ansprüche 1 bis 8, bei dem der Dehydrierungskatalysator ein Element ausgewählt aus der Gruppe 10 des Periodensystems der Elemente oder eine Verbindung davon umfasst.

10. Verfahren nach einem der Ansprüche 1 bis 9, bei dem die Dehydrierungsbedingungen in (b) eine Temperatur von 200°C bis 600°C und einen Druck von 100 kPa bis 3550 kPa (atmosphärischen Druck bis 500 psig) einschließen.

Revendications

1. Procédé de production de composés biphényliques substitués par méthyle, le procédé comprenant :

(a) la mise en contact d'une charge comprenant au moins un hydrocarbure aromatique choisi dans le groupe constitué du toluène et de mélanges de toluène et de xylène avec de l'hydrogène en présence d'un catalyseur d'hydroalkylation comprenant un composant acide et un composant d'hydrogénation, dans des conditions efficaces pour produire un produit de réaction d'hydroalkylation comprenant des (méthylcyclohexyl)toluènes ; et

(b) la déshydrogénation d'au moins une partie du produit de réaction d'hydroalkylation en présence d'un catalyseur de déshydrogénation dans des conditions efficaces pour produire un produit de réaction de déshydrogénation comprenant un mélange de composés biphényliques substitués par méthyle,

dans lequel le composant acide du catalyseur d'hydroalkylation comprend un tamis moléculaire, dans lequel le tamis moléculaire comprend un tamis moléculaire de la famille MCM-22.

2. Procédé selon la revendication 1, comprenant en outre :

(c) la mise en contact d'au moins une partie du produit de réaction de déshydrogénation avec un oxydant dans des conditions efficaces pour convertir au moins une partie des composés biphényliques substitués par méthyle en acides biphénylcarboxyliques ; et

(d) la réaction des acides biphénylcarboxyliques avec un ou plusieurs alcools en C₄ à C₁₄ dans des conditions efficaces pour produire des esters biphényliques.

3. Procédé selon l'une quelconque des revendications 1 à 2, dans lequel le composant d'hydrogénation du catalyseur d'hydroalkylation est choisi dans le groupe constitué des palladium, ruthénium, nickel, zinc, étain, cobalt et des composés et des mélanges de ceux-ci.

4. Procédé selon l'une quelconque des revendications 1 à 3, dans lequel les conditions dans la mise en contact (a) comprennent une température de 100 °C à 400 °C et une pression de 100 à 7 000 kPa.

5. Procédé selon l'une quelconque des revendications 1 à 4, dans lequel le rapport molaire de l'hydrogène à la charge aromatique introduite dans la mise en contact (a) est de 0,15:1 à 15:1.

6. Procédé selon l'une quelconque des revendications 1 à 5, dans lequel l'hydrocarbure aromatique est le toluène et le produit de réaction d'hydroalkylation comprend moins de 30 % en poids de méthylcyclohexane et moins de 2 % de composés de diméthylbi(cyclohexane) .

7. Procédé selon l'une quelconque des revendications 1 à 6, dans lequel l'hydrocarbure aromatique est le toluène et le produit de réaction d'hydroalkylation comprend moins de 1 % en poids de composés contenant plus de 14 atomes de carbone.

8. Procédé selon l'une quelconque des revendications 1 à 7, dans lequel la charge comprend en outre du benzène et/ou au moins un alkylbenzène différent du toluène et du xylène.

9. Procédé selon l'une quelconque des revendications 1 à 8, dans lequel le catalyseur de déshydrogénation comprend un élément ou un composé de celui-ci choisi parmi le groupe 10 de la table périodique des éléments.

10. Procédé selon l'une quelconque des revendications 1 à 9, dans lequel les conditions de déshydrogénation dans (b) comprennent une température de 200 °C à 600 °C et une pression de 100 kPa à 3550 kPa (atmosphérique à 500 psig).

Drawing